The present invention relates to electromagnetic transducers, which may for example be employed in thin film inductive write heads of the type formed on the trailing ends of air bearing sliders used in magnetic recording disk drives.
An inductive transducer used for writing and/or reading magnetic information on storage media, such as a disk or tape, typically includes electrically conductive coil windings that encircle a magnetic core. The magnetic core has leading and trailing pole layers. The pole layers have pole tip portions adjacent to the recording media. The magnetic core is interrupted by a submicron nonmagnetic gap disposed between the pole tip portions to divert magnetic flux to the media during writing. To write to the media, electric current is flowed through the coil windings, which produces magnetic flux in the core encircling the coil windings, the magnetic flux fringing across the nonmagnetic gap adjacent to the media so as to write bits of magnetic field information in tracks on the recording media.
The leading pole layer is typically substantially flat, whereas the trailing pole layer can be curved in order to cover coil windings and insulation disposed between the pole layers. Alternatively, the trailing pole layer can be flat if a pedestal adjacent to the recording media is magnetically coupled to either the leading or the trailing pole layer. In that case, the submicron nonmagnetic gap is located between the pedestal and the pole layer to which it is not magnetically coupled.
The width of the pole tip portion, which corresponds to the track width, may be decreased to allow more tracks to be written on the recording media. As track width is decreased, however, it becomes more difficult to transmit high-intensity magnetic flux through the pole tip portion. A standard technique for increasing the strength of the magnetic field at the pole tip surface has been to increase the magnetic moment of the material near both the pole tip surface and the recording gap. One way to accomplish this is to form a pedestal of material having a high magnetic moment between a pole layer and the recording gap, increasing the magnetic field at the edge of the pole tip surface adjoining the gap.
As noted above, the trailing pole layer and/or pedestal may have a flared or tapered width near the region around the pole tip surface in which the sides are parallel. Various geometries of tapered pole layers near the pole tip portions have been used, such as the geometries depicted in FIGS. 2A–2D. In all of the geometries shown in FIGS. 2A–2D, the sides 80 immediately adjacent to the pole tip surfaces 82 are parallel. In each of the geometries, after a flare point 84, the width of the pole layer increases more or less at a steady rate extending away from the pole tip surface 82. It is also possible that tapered pole layers may have curved regions adjacent pole tip sides.
FIG. 2C is an attempt to replicate the shape of a pole layer disclosed in U.S. Pat. No. 6,055,137 to Ishiwata et al. Ishiwata et al. teach that when the width of the pole-like distal end portion of the other magnetic pole decreases, the magnetic anisotropy of the other magnetic pole becomes difficult to form, and tends to be formed in an undesirable direction. Ishiwata et al. avoid that undesirable magnetic anisotropy by shaping the pole tip with a focused ion beam (FIB) that ablates parts of a trailing pole tip. The “recessed portions” that remain adjacent the pole tip would disrupt the air-bearing surface, however, as well being difficult to form. Moreover, should the FIB be slightly misdirected and cut into the leading pole tip, the etched corners of the leading pole layer may create funnels for off-track flux.